Correction of Excessive Anticoagulation with Low-Dose Oral Vitamin K_1

Abstract

Despite earlier acceptance of oral vitamin K₁ (phytonadione) for the treatment of excessive anticoagulation, some recent guidelines do not recommend its use. To reevaluate the efficacy of oral vitamin K₁ in correcting excessive anticoagulation. Case series. Anticoagulation clinics at two university medical centers. 81 outpatients who had an international normalized ratio (INR) greater than 5.0 but did not have significant bleeding. Withholding 1 or 2 doses of warfarin, administering 2.5 mg of oral vitamin K₁, measuring the INR after 24 to 48 hours, and adjusting the warfarin dose. INRs were obtained from a portable capillary fingerstick monitor or from an automated photooptical coagulometer. In 68 of 71 patients (96%), oral vitamin K₁ lowered the INR from between 5.0 and 10.0 to less than 5.0 without inducing resistance to further anticoagulation. Withholding 1 or 2 doses of warfarin and administering 2.5 mg of oral vitamin K₁ is a reliable, safe, and inexpensive way to rapidly correct excessive anticoagulation (INR > 5.0) in patients who do not have serious bleeding episodes and have an INR of less than 10.0.